JEE Main & Advanced Mathematics Applications of Derivatives Question Bank Application in Mechanics and Rate Measurer

  • question_answer
    If the law of motion in a straight line is \[s=\frac{1}{2}v\,t,\] then acceleration is [MP PET 1991]

    A)            Constant

    B)            Proportional to t

    C)            Proportional to v

    D)            Proportional to s

    Correct Answer: A

    Solution :

               \[s=\frac{1}{2}vt\] Þ \[2s=vt\]Þ \[2\frac{ds}{dt}=v+t.\frac{dv}{dt}\]                    Þ \[2\frac{{{d}^{2}}s}{d{{t}^{2}}}=\frac{dv}{dt}+t.\frac{{{d}^{2}}v}{d{{t}^{2}}}+\frac{dv}{dt}\]                    But \[\frac{dv}{dt}\]= acceleration                    Þ   \[2a=a+t.\frac{da}{dt}+a\] Þ\[\frac{da}{dt}=0\] or \[xy=4\times 4=16\]            But for whole notation \[t=0\]is impossible so that \[\frac{da}{dt}=0\] i.e., a is constant.


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